1. Field of the Invention
The present invention relates to an insulation-displacement terminal fitting.
2. Description of the Related Art
Japanese Examined Patent Publication No. 57-10550 discloses an insulation-displacement terminal fitting with opposed left and right side walls and a wire-receiving space therebetween. Portions of the respective side walls are bent to define V-shaped insulation-displacement portions that project into the wire-receiving space. A wire can be pushed into the wire-receiving space in a direction normal to the longitudinal direction of the wire. As a result, an insulation coating of the wire is cut open by projecting ends of the insulation-displacement portions and a core of the wire is brought into contact with the projecting ends of the insulation-displacement portions.
The contact area between the insulation-displacement portions and the core is increased and the contact reliability is better as the angle at the projecting ends of each V-shaped insulation-displacement portion increases. However, a pulling force may be exerted on the wire in its longitudinal direction, and such a pulling force may cause a loose movement of the wire. The ability of the wire to resist such a pulling force is greater when the angle of the insulation-displacement portion to the cut surface of the resin coating becomes closer to a right angle with respect to the pulling direction and when the angle at the projecting ends of the V-shaped insulation-displacement portions is smaller.
Typically these competing objectives of achieving contact reliability with the core and restricting loose movement of the wire has required one of these objectives to be compromised so that the other objective can be achieved more effectively.
In view of the above, an object of the invention is to improve contact reliability with a core and to restrict loose movement of a wire.
The invention is directed to an insulation-displacement terminal fitting having opposed first and second side walls and a wire-receiving space therebetween. First and second insulation-displacement portions project inwardly from the respective side walls. A wire may be oriented substantially parallel to the respective side walls and may be pushed substantially normal to the longitudinal direction of the wire into the wire-receiving space between the insulation-displacement portions. Thus, a resin coating of the wire is cut open by projecting ends of the insulation-displacement portions, and a core of the wire is brought into contact with the projecting ends of the insulation-displacement portion. Each insulation-displacement portion is formed by first and second plates that are bent from the corresponding side wall to project substantially in a V-shape into the wire-receiving space. The bending angle between at least one of the plates of the first of the insulation-displacement portion and the first side wall is set larger than a bending angle between the plates of the second insulation-displacement portion and the second side wall. Additionally, the two plates of one of the insulation-displacement portions are bent from the corresponding side wall to define different bending angles on that insulation displacement portion.
One plate of at least one insulation-displacement portion may be at a right angle to the corresponding side wall. Additionally or alternatively, one plate of at least one insulation-displacement portion may be at an acute angle to the corresponding side wall.
An external pulling force could be exerted on the wire in a direction that would loosely move the wire in its longitudinal direction. Effective loose movement restriction can be obtained by setting the plate that faces away from the direction of the pulling force at close to a right angle with respect to the side wall. The plate that faces in the same direction as the pulling force on the wire then can be set at a large angle, i.e. at an obtuse angle, with respect to the side wall. Accordingly, a bending angle between the plates of the insulation-displacement portion is large, and a wide contact area with the core is achieved.
The plate that faces away from the direction of the pulling force on the wire is at close to a right angle to the side wall. Thus, that plate is engaged with a cut surface of the resin coating is aligned in a direction normal to the direction of loose movement, and a high loose movement restricting effect can be obtained.
The plate that faces away from the direction of the pulling force on the wire also may be at an acute angle to the side wall, and hence bites in the resin coating like a wedge. Thus, a high loose movement restricting effect can be obtained.